Dielectric constant epsilon', loss tan delta and ac conductivity sigma of ZnF2-Bi2O3-TeO2 glasses with varying concentrations of Bi2O3 (from 5 to 20%) are studied as a function of frequency and temperature over moderately wide ranges. The dielectric breakdown strength for these glasses is also determined in air medium. From the analysis of these studies along with the IR spectra & DTA recordings of these glasses, the structural changes in ZnF2-Bi2O3-TeO2 glass system with change in the concentration of Bi2O3, are discussed.